1. Field of the Invention
This invention relates to a method of continuously manufacturing a molded surface fastener member and the molded surface fastener member manufactured by the method, which has a multiplicity of engaging elements standing on a front surface of a substrate sheet, by continuous injection molding using thermoplastic resin, and more particularly to a molded surface fastener member manufacturing method and the molded surface fastener member manufactured by the method, which is hard either to tear or to expand or which is expected to shield an electromagnetic wave.
2. Description of the Related Art
Generally, in this type molded surface fastener member in which a substrate sheet and a multiplicity of engaging elements are integrally and continuously molded from thermoplastic synthetic resin, orientation of molecules tends to occur in the longitudinal direction so that the surface fastener member tends to be torn in the longitudinal direction. Particularly in the case of soft synthetic resin, the material tends to excessively expand during molding so that the resulting substrate sheet tends to become wavy or puckered and hence would not be stable in shape, thus deteriorating the quality of products and causing a large difference in strength between the longitudinal direction and the transverse direction.
Since the conventional molded surface fastener member is merely continuously molded from thermoplastic resin, it tends to expand when it is pulled while being cut into pieces of the final product length, causing errors in size of the final products. Further, when the thus manufactured surface fastener member is attached to a garment by sewing, the substrate sheet tends to be torn due to the sewing needle so that occasionally an appropriate sewing operation cannot be achieved.
In view of the foregoing problems, Japanese Patent Laid-Open Publication No. 7-184707 discloses a method in which a molten resin is continuously injected directly from an injection nozzle to a circumferential surface of a die wheel having a multiplicity of engaging-element forming cavities and being driven to rotate, and simultaneously at least a fiber thread is introduced into a gap between the die wheel and the injection nozzle linearly or in a zigzag pattern, so as to embed the fiber thread integrally in the substrate sheet at the time of molding the substrate sheet and engaging elements.
However, in the molded surface fastener member which is manufactured by the method disclosed in the foregoing publication, the position of the thread embedded in the substrate sheet is inevitably off to the side having the engaging elements. Therefore, though the substrate sheet can be prevented from being expanded excessively, a resin material composing the substrate sheet where the fiber thread is embedded becomes extremely thin so that the substrate sheet tends to be torn along the fiber thread, thus the expected results cannot be achieved.
Further, since the fiber thread is made of a resin material, the resulted molded surface fastener member tends to be influenced by an electromagnetic wave, thus such surface fastener member is not suitable for a member to join parts which should not be influenced.